A wide-angle, large-aperture, fixed-focus lens

Abstract

The present invention discloses a wide-angle large-aperture fixed-focus lens, belonging to the technical field of optical lenses. From the object plane to the image plane, it includes a first lens group, a diaphragm, and a second lens group. Among them, the first lens group includes a first negative meniscus lens, a second convex-concave lens, a third convex-concave lens, a fourth convex-concave lens, and a fifth positive meniscus lens; the second lens group includes a sixth double-convex lens, a seventh convex-concave lens, an eighth double-convex lens, a ninth double-concave lens, and a tenth double-convex lens. This fixed-focus lens satisfies: 10mm < EFL < 20mm; Fno < 2; 1 < EFL / BFL < 2. The present invention can achieve miniaturization, high performance, large aperture, and low cost, and the angle of view can reach 100 degrees.

Description

Technical Field

[0001] The present invention relates to the technical field of lenses, and particularly to a wide-angle large-aperture fixed-focus lens. Background Art

[0002] Because of its larger viewing angle, the wide-angle lens has a larger imaging range and is applied in the fields of security, photography, etc. With the continuous development of detector technology and the update and iteration of electronic devices, higher requirements are put forward for the miniaturization and light transmittance of wide-angle lenses.

[0003] A Chinese patent with the publication number CN113253420A relates to a lens. Among them, the fixed-focus lens sequentially includes from the object side: a first lens group with positive optical power, a diaphragm, and a second lens group with positive optical power. The fixed-focus lens satisfies 22mm < EFL < 30mm; Fno < 1.3; 1 < EFL / BFL < 2; where EFL is the overall focal length of the fixed-focus lens, Fno is the relative aperture of the fixed-focus lens, and BFL is the optical back focal length of the fixed-focus lens. Although this structure realizes a large-aperture design, the number of lenses reaches ten, and the back intercept is short, increasing the possibility of high focusing sensitivity of the lens. Summary of the Invention

[0004] In view of this, the present invention provides a wide-angle large-aperture fixed-focus lens. Through reasonable design optimization, with as few lenses as possible, it realizes as large and appropriate a back focal length as possible. While achieving an F number less than 2, it adopts a surface shape that can be processed by conventional techniques, facilitating the low-cost processing of the lens.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A wide-angle large-aperture fixed-focus lens sequentially includes from the object side to the image side along the optical axis: a first lens group with positive optical power, a diaphragm, and a second lens group with positive optical power; within the first lens group, from the object side to the image side along the optical axis, it sequentially includes a first negative meniscus lens with negative optical power, a second concave-convex lens with negative optical power, a third concave-convex lens with positive optical power, a fourth concave-convex lens with positive optical power, and a fifth positive meniscus lens with positive optical power; within the second lens group, from the object side to the image side along the optical axis, it sequentially includes a sixth double-convex lens with negative optical power, a seventh concave-convex lens with negative optical power, an eighth double-convex lens with positive optical power, a ninth double-concave lens with negative optical power, and a tenth double-convex lens with positive optical power;

[0007] Each of the first to tenth lenses includes an object surface facing the object side and allowing imaging light to pass through and an image surface facing the image side and allowing imaging light to pass through. At least one surface of the second, third, fourth, and ninth lenses is an even aspherical surface;

[0008] The fixed-focus lens satisfies the following conditions:

[0009] 10mm <EFL<20mm;

[0010] Fno<2;

[0011] 1 <EFL / BFL<2;

[0012] Among them, EFL is the overall focal length of the fixed-focus lens, Fno is the relative aperture of the fixed-focus lens, and BFL is the optical back focus of the fixed-focus lens.

[0013] Furthermore, the image plane of the fourth meniscus lens and the object plane of the fifth positive meniscus lens are glued to each other; the image plane of the sixth biconvex lens and the object plane of the seventh meniscus lens are glued to each other.

[0014] Further, the first negative meniscus lens has a negative refractive power, the object surface of the first negative meniscus lens is convex, and the image surface is concave; the second meniscus lens has a negative refractive power, the object surface of the second meniscus lens is concave, and the image surface is concave; the third meniscus lens has a positive refractive power, the object surface of the third meniscus lens is concave, and the image surface is convex; the fourth meniscus lens has a positive refractive power, the object surface of the fourth meniscus lens is concave, and the image surface is convex; the fifth positive meniscus lens has a positive refractive power, and the object surface of the fifth positive meniscus lens is convex , the image plane is concave; the sixth biconvex lens has negative refractive power, the object plane of the sixth biconvex lens is convex, and the image plane is convex; the seventh concave-convex lens has negative refractive power, the object plane of the seventh concave-convex lens is concave, and the image plane is convex; the eighth biconvex lens has positive refractive power, the object plane of the eighth biconvex lens is convex, and the image plane is convex; the ninth biconcave lens has negative refractive power, the object plane of the ninth biconcave lens is concave, and the image plane is concave; the tenth biconvex lens has positive refractive power, the object plane of the tenth biconvex lens is convex, and the image plane is convex.

[0015] Furthermore, among the ten surfaces of the five lenses of the first lens group, at least three surfaces are aspherical surfaces, and the curvature radius of at least two aspherical surfaces is less than 0, and the curvature radius of at least one aspherical surface is greater than 0.

[0016] Furthermore, among the ten surfaces of the five lenses of the second lens group, at least one surface is an aspherical surface, and the curvature radius of at least one aspherical surface is greater than 0.

[0017] Further, all surfaces of the first negative meniscus lens are curved toward the image side, and all surfaces of the fifth positive meniscus lens are curved toward the image side.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention realizes the function of a wide-angle and large-aperture lens, and the aperture number (i.e., F-number) of the lens is less than 2.

[0020] 2. Through reasonable optimization, the number of lenses of the present invention does not exceed ten, and the back focal length is further improved, reducing the possibility of excessive focusing sensitivity of the wide-angle and large-aperture lens.

[0021] 3. The fixed-focus lens of the present invention satisfies the following conditions: 10mm < EFL < 20mm; Fno < 2; 1 < EFL / BFL < 2; the working wavelength band of the fixed-focus lens is 0.48μm to 0.65μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic cross-sectional structure diagram of the wide-angle and large-aperture fixed-focus lens in the embodiment of the present invention.

[0023] Figure 2 It is a schematic diagram of the MTF curve of the wide-angle and large-aperture fixed-focus lens in the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings, and other embodiments can be obtained.

[0025] In order to make the drawings concise, only the parts related to the invention are schematically shown in each drawing, and they do not represent their actual structures as products.

[0026] In the following description, the image plane (IMG) refers to the plane on which the image formed by passing through the lens is located, and the image side may refer to the direction where the imaging element such as an image sensor is arranged. Based on the lens, the object side and the image side may refer to opposite directions.

[0027] The present invention will be further described in detail below with reference to the accompanying drawings.

[0028] As Figure 1 shown, a wide-angle and large-aperture fixed-focus lens includes, in sequence along an optical axis from the object plane to the image side, a first lens group L1 with negative optical power, a diaphragm 6, a second lens group L2, and an image plane 12. The image plane 12 is a CCD or CMOS element.

[0029] In this embodiment, the optical system includes, in order from the object plane to the image side, a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, an aperture 6, a sixth lens 7, a seventh lens 8, an eighth lens 9, a ninth lens 10, a tenth lens 11, and an image plane 12. The first to tenth lenses each include an object plane facing the object side and allowing imaging light to pass therethrough, and an image plane facing the image side and allowing imaging light to pass therethrough.

[0030] In this embodiment, the first lens group L1 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, and a fifth lens 5; the second lens group L2 includes a sixth lens 7, a seventh lens 8, an eighth lens 9, a ninth lens 10, and a tenth lens 11.

[0031] Furthermore, the aspheric surface equations of the third lens, the fourth lens and the eleventh lens are as follows:

[0032]

[0033] Among them, z represents the distance of the surface from the vertex in the direction of the optical axis, c represents the curvature of the vertex, K represents the quadratic surface coefficient, h represents the distance from the optical axis to the surface, and B, C, D, and E represent the fourth-order, sixth-order, eighth-order, and tenth-order surface coefficients, respectively.

[0034] In this embodiment, the optical system composed of the above lenses achieves the following optical indicators:

[0035] Focal length: f=16mm;

[0036] Relative aperture F: 1.8;

[0037] Field of view: 2ω≥100°;

[0038] Total optical path length ≤115mm, optical intercept ≥31mm;

[0039] Use band range: 0.48μm~0.65μm.

[0040] The detailed optical data of this embodiment are shown in the following table:

[0041] surface type Radius of curvature thickness Refractive Index Dispersion coefficient focal length 1 Spherical 37.182 4 1.73 51.5 -41.332 2 Spherical 15.946 13.4 3 Aspheric -51.919 1.5 1.81 25.5 -25.467 4 Spherical 34.329 4.5 5 Aspheric -333.596 4.7 1.85 23.8 128.806 6 Spherical -31.294 4.7 1.53 60.2 57.240 7 Spherical -70.453 2.8 8 Spherical 33.150 5 1.65 33.9 60.862 9 Spherical 196.061 16.1 Aperture Spherical Infinity 6.4 11 Spherical 70.421 5 1.59 68.3 -94.660 12 Spherical -18.513 1.5 1.95 32.3 -167.540 13 Spherical -71.556 0.2 14 Spherical 36.478 5 1.62 53.9 31.040 15 Spherical -38.237 2.5 16 Aspheric -42.709 2 1.61 37.0 -28.286 17 Spherical 29.718 1.1 18 Spherical 44.045 3.8 1.66 54.7 33.374 19 Spherical -43.152 31.3 IMA Imaging surface Infinity

[0042] The first lens has a negative refractive power, and the object surface of the first lens is a convex surface and the image surface is a concave surface;

[0043] The second lens has negative refractive power, and the object surface of the second lens is concave and the image surface is concave; the third lens has positive refractive power, and the object surface of the third lens is concave and the image surface is convex; the fourth lens has positive refractive power, and the object surface of the fourth lens is concave and the image surface is convex; the fifth lens has positive refractive power, and the object surface of the fifth lens is convex and the image surface is concave; the sixth lens has negative refractive power, and the object surface of the sixth lens is convex and the image surface is convex; the seventh lens has negative refractive power, and the object surface of the seventh lens is concave and the image surface is convex; the eighth lens has positive refractive power, and the object surface of the eighth lens is convex and the image surface is convex; the ninth lens has negative refractive power, and the object surface of the ninth lens is concave and the image surface is concave; the tenth lens has positive refractive power, and the object surface of the tenth lens is convex and the image surface is convex; the wide-angle large aperture fixed focus lens has ten lenses with refractive power.

[0044] The first negative meniscus lens adopts an optical material with a refractive index greater than 1.7 and less than 2 in the visible light band, and an Abbe constant greater than 50 and less than 52. The second meniscus lens adopts an optical material with a refractive index greater than 1.8 and less than 2 in the visible light band, and an Abbe constant greater than 25 and less than 27. The third meniscus lens adopts an optical material with a refractive index greater than 1.8 and less than 2 in the visible light band, and an Abbe constant greater than 23 and less than 25. The fourth meniscus lens adopts an optical material with a refractive index greater than 1.5 and less than 2 in the visible light band, and an Abbe constant greater than 60 and less than 62. The fifth positive meniscus lens adopts an optical material with a refractive index greater than 1.6 and less than 2 in the visible light band, and an Abbe constant greater than 33 and less than 35. The sixth biconvex lens adopts an optical material with a refractive index greater than 1.5 and less than 2 in the visible light band, and an Abbe constant greater than 68 and less than 10. The seventh meniscus lens adopts an optical material with a refractive index greater than 1.9 and less than 2 in the visible light band, and an Abbe constant greater than 32 and less than 34. The eighth biconvex lens adopts an optical material with a refractive index greater than 1.6 and less than 2 in the visible light band, and an Abbe constant greater than 53 and less than 55. The ninth biconcave lens adopts an optical material with a refractive index greater than 1.6 and less than 2 in the visible light band, and an Abbe constant greater than 36 and less than 38. The tenth biconvex lens adopts an optical material with a refractive index greater than 1.6 and less than 2 in the visible light band, and an Abbe constant greater than 54 and less than 56.

[0045] The image plane of the third lens and the object plane of the fourth lens are glued to each other, and the image plane of the sixth lens and the object plane of the seventh lens are glued to each other.

[0046] The second lens, the third lens, the fourth lens and the ninth lens have one surface which is an even-order aspherical surface.

[0047] Among them, the second lens is aspherical near the object surface:

[0048] c=1 / R, R=-51.919, K=0, B=-4.486e-6, C=3.938e-9, D=-4.670e-11, E=2.709e-15.

[0049] Among them, the third lens is aspherical near the object surface:

[0050] c=1 / R, R=-333.596, K=0, B=4.480e-6, C=8.427e-10, D=4.164e-11, E=-4.040e-14.

[0051] Among them, the fifth lens is aspherical near the object surface:

[0052] c=1 / R, R=33.150, K=0, B=1.443e-6, C=2.735e-9, D=8.195e-13, E=2.985e-15.

[0053] Among them, the ninth lens is aspherical near the object surface:

[0054] c=1 / R, R=-42.709, K=0, B=-1.230e-6, C=1.318e-8, D=-8.078e-11, E=0.

[0055] Figure 2 The optical transfer function results of this embodiment are shown.

[0056] In summary, compared with the prior art, the present invention has a smaller number of lens elements, and the aperture number (ie, F number) of the lens is less than 2. The present invention can achieve miniaturization, high performance, large aperture, and low cost, and the picture angle can reach 100 degrees.

Claims

1. A wide-angle, large-aperture, fixed-focus lens, comprising, from the object side to the image side, a first lens group with positive focal power, a stop, and a second lens group with positive focal power in sequence along the optical axis; characterized in that: The first lens group includes, from the object side to the image side along the optical axis, a first negative meniscus lens with negative optical power, a second meniscus lens with negative optical power, a third meniscus lens with positive optical power, a fourth meniscus lens with positive optical power, and a fifth positive meniscus lens with positive optical power; the second lens group includes, from the object side to the image side along the optical axis, a sixth biconvex lens with negative optical power, a seventh meniscus lens with negative optical power, an eighth biconvex lens with positive optical power, a ninth biconcave lens with negative optical power, and a tenth biconvex lens with positive optical power; The first to tenth lenses each include an object surface facing the object side and allowing imaging light to pass through, and an image surface facing the image side and allowing imaging light to pass through, and the second, third, fourth and ninth lenses each include at least one surface that is an even-order aspheric surface; The fixed-focus lens meets the following conditions: 10mm <EFL<20mm; Fno<2; 1 <EFL / BFL<2; Among them, EFL is the overall focal length of the fixed-focus lens, Fno is the relative aperture of the fixed-focus lens, and BFL is the optical back focus of the fixed-focus lens.

2. The wide-angle, large-aperture, fixed-focus lens according to claim 1, characterized in that: The image plane of the third meniscus lens and the object plane of the fourth meniscus lens are glued to each other; the image plane of the sixth biconvex lens and the object plane of the seventh meniscus lens are glued to each other.

3. The wide-angle, large-aperture, fixed-focus lens according to claim 1, characterized in that: The first negative meniscus lens has a negative refractive power, and the object surface of the first negative meniscus lens is convex and the image surface is concave; the second meniscus lens has a negative refractive power, and the object surface of the second meniscus lens is concave and the image surface is convex; the third meniscus lens has a positive refractive power, and the object surface of the third meniscus lens is concave and the image surface is convex; the fourth meniscus lens has a positive refractive power, and the object surface of the fourth meniscus lens is concave and the image surface is convex; the fifth positive meniscus lens has a positive refractive power, and the object surface of the fifth positive meniscus lens is convex and the image surface is is concave; the sixth biconvex lens has negative refractive power, the object surface of the sixth biconvex lens is convex, and the image surface is convex; the seventh meniscus lens has negative refractive power, the object surface of the seventh meniscus lens is concave, and the image surface is convex; the eighth biconvex lens has positive refractive power, the object surface of the eighth biconvex lens is convex, and the image surface is convex; the ninth biconcave lens has negative refractive power, the object surface of the ninth biconcave lens is concave, and the image surface is concave; the tenth biconvex lens has positive refractive power, the object surface of the tenth biconvex lens is convex, and the image surface is convex.

4. The wide-angle, large-aperture, fixed-focus lens according to claim 1, characterized in that: Among the ten surfaces of the five lenses of the first lens group, at least three surfaces are aspherical surfaces, and the curvature radius of at least two aspherical surfaces is less than 0, and the curvature radius of at least one aspherical surface is greater than 0.

5. The wide-angle, large-aperture, fixed-focus lens according to claim 1, characterized in that: Among the ten surfaces of the five lenses of the second lens group, at least one surface is an aspherical surface, and the curvature radius of at least one aspherical surface is greater than 0.

6. The wide-angle, large-aperture, fixed-focus lens according to claim 1, characterized in that: All surfaces of the first negative meniscus lens are curved toward the image side, and all surfaces of the fifth positive meniscus lens are curved toward the image side.

Images